Photoflash lamp



Nov. 17, 1970 J. w. SHAFFER ETAL 3,540,819

PHOTOFLASH LAMP Filed Aug.'30, 1968 INVENTORS JOHN w. SHAFFER STEPHEN v. BROWN ATTORN EYE nited States Patent 3,540,819 PHOTOFLASH LAMP John W. Shaffer and Stephen V. Brown, Williamsport, Pa., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Aug. 30, 1968, Ser. No. 756,515 Int. Cl. F21k /02 U.S. Cl. 431-93 5 Claims ABSTRACT OF THE DISCLOSURE A percussive-type photofiash lamp in which a stainless steel wire is used as the anvil in the primer thereof.

This invention relates to the manufacture of photofiash lamps and more particularly those of the percussive type.

Generally speaking a percussive-type photofiash lamp comprises an hermetically sealed, light-transmitting envelope containing a source of actinic light and having a primer secured thereto. More particularly, the percussivetype photofiash lamp may comprise a length of glass tubing constricted to a tip at one end thereof and having a primer sealed therein at the other end thereof. The length of glass tubing which defines the lamp envelope contains a combustible such as shredded zirconium foil and a combustion-supporting gas such as oxygen. The primer may comprise a metal tube and a charge of fulminating material on a wire anvil supported therein. Operation of the lamp is initiated by an impact onto the tube of the primer to cause deflagration of the fulminating material on the wire anvil up through the tube to ignite the combustible disposed in the lamp envelope.

Heretofore the wire anvil has been fabricated from soft iron, particularly since iron is sufliciently resilient to be readily shaped for self support within the metal tube of the primer and is readily etched so as to provide a rough surface for adherence of the fulminating material. However, the use of iron as the material for a Wire anvil in percussive-type photofiash lamps presents several problems. The etched surface rusts very rapidly in contact with air and the etching process is difiicult to control. In addition, iron catalytically promotes slow oxidation of red phosphorous which, in the presence of potassium chlorate, is the impact-sensitive ingredient of the fulminating material. Such oxidative degradation of the fulminating material greatly reduces the reliability of percussive-type photofiash lamps.

Copper or brass wire anvils are not satisfactory because copper is even more active in promoting phosphorous oxidation than is iron. Nickel wire does not provide a satisfactory surface upon etching to promote good adhesion of the fulminating material. Wires of many other metals are either low melting, too combustible in oxygen, too soft to be held in place by undulations or are prohibitively expensive.

In view of the foregoing, one of the principal objects of this invention is to provide a wire anvil for percussivetype photofiash lamps that promotes excellent adhesion of the fulminating material thereto and which increases the impact sensitivity and ignition reliability for such lamps.

Another object is to provide a wire anvil for percussivetype photofiash lamps that is chemically compatible with and noncontaminating toward the fulminating material.

3,540,819 Patented Nov. 17, 1970 'ice These and other objects, advantages and features are attained, in accordance with the principles of this invention, by the use of wet hydrogen treated stainless steel wire anvils in percussive-type photofiash lamps.

In the specific embodiment of this invention illustrated in the accompanying drawings, the figure is an elevational view partly in section of a percussive-type photofiash lamp with which the wire anvil of this invention may be employed. The lamp comprises a length of glass tubing defining an hermetically sealed lamp envelope 2 constricted at one end to define an exhaust tip 4 and shaped to define a press 6 at the other end thereof. A primer 8 is sealed in the press 6. The primer 8 comprises a metal tube 10, a wire anvil 12 and a charge of fulminating material 14 which comprises a mixture of red phosphorous, potassium chlorate, a metallic fuel such as powdered boron, zirconium, silicon or the like or combination thereof and a resin binder such as hydroxyethyl cellulose or nitrocellulose.

The end of the tube 10 located outsidethe lamp envelope is closed whereas the other end, which is located inside the lamp envelope, is open. The wire 12 is frictionally held in place by undulations 13. The charge of fulminating material 14 is located on that segment of the wire 12 which is located in the exposed segment of the tube 10. A combustible such as filamentary zirconium 18 and a combustion-supporting gas such as oxygen are disposed Within the lamp envelope 2.

We have found that stainless steels, with a high chromium content, such as the 300 series for example, are inert toward the fulminating material and thus help to promote good shelf life. The stainless anvil wire is not subject to rusting and corrosion, and is sufficiently tough and resilient to permit positive anchoring in the metal tube 10 of the primer -8. We have also found that an excellent surface for bonding of the fulminating material can be produced by heating of the wire in an atmosphere of moist hydrogen. Such treatment results in the formation of a black velvet-like coating of chromium oxides. This oxide film is insoluble and is therefore nonreactive toward the fulminating material.

We have also found that lamp flashing reliability and impact sensitivity are better with such treated stainless steel anvil wires than with etched iron anvil wires.

Generally speaking, improved results are obtainable with any chromium-containing alloys that can be treated so as to produce a velvety coating of chromium oxides and that are chemically compatible with the phosphorous in the fulminating material. Some examples of applicable materials are No. 4 alloy, and types 302, 303, 304, 305 and 316 stainless steels.

What we claim is:

1. A photofiash lamp comprising: an hermetically sealed, light-transmitting envelope; a quantity of filamentary combustible material located within said envelope; a combustion-supporting gas in said envelope; and a primer secured to and extending from one end of said envelope and in communication therewith, said primer comprising a metal tube, a wire anvil disposed in said tube and a quantity of fulminating material on said anvil, said wire anvil being chemically compatible with and noncontaminating toward said fulminating material.

2. The combination of claim 1 in which said wire anvil is of stainless steel.

3. The combination of claim 1 in which said wire anvil References Cited is of stainless steel having a high chromium content. UNITED STATES PATENTS 4. The combination of claim 1 in which the surface of said wire anvil has a velvet-like coating of chromium g; E33 Ides 5 3,046,769 7/1962 Anderson et a1. 431 95 5. The combination of claim 1 in which the wire anvil is No. 4 alloy. EDWARD J. MICHAEL, Primary Examiner 

